In that case, an absolute scale is a system of measurement that begins at a minimum, or zero point, and progresses in only one direction.
An absolute scale begins at a natural minimum, leaving only one direction in which to progress.
An absolute scale can only be applied to measurements in which a true minimum is known to exist.
Time, for example, which does not have a clearly known beginning, is measured on a relative scale, with an arbitrary zero-point such as the conventional date of the birth of Jesus (see Anno Domini) or the accession of an emperor.
Absolute scales are used when precise values are needed in comparison to a natural, unchanging zero point.